Any immigration attorney should be able to help you with this - it shouldn't matter if they're in Massachusetts or not. Just try to find one that has some experience of tech start ups. I've had a few conversations with https://startupimmigrationattorney.com/ and I was pretty happy with them, although we didn't actually make any applications for anything.
I believe that with E visas, the company has to be mainly owned by citizens of the treaty country (not US, iow) so with the 50% ownership I'm not sure if that will work.
Are you sure that your bids require everyone to have US work authorization? For comparison, my organization has people working from Europe and people on US visas all working on the same contracts - only the people who live in or travel to the US need visas. And these are often public sector contracts. I've never heard anything about European based staff not being able to contribute.
I believe that with E visas, the company has to be mainly owned by citizens of the treaty country (not US, iow) so with the 50% ownership I'm not sure if that will work.
Are you sure that your bids require everyone to have US work authorization? For comparison, my organization has people working from Europe and people on US visas all working on the same contracts - only the people who live in or travel to the US need visas. And these are often public sector contracts. I've never heard anything about European based staff not being able to contribute.